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Wall Connector - max run for 6/2 Romex on 50A breaker

Aug 22, 2021
5
1
Harrisburg, PA
What is the maximum length of 6/2 romex for a wall connector on a 50A breaker? Is there a chart or reference I could use?

I'm installing a Tesla Wall Connector (3rd Gen) in preparation for my Model Y delivery in a couple weeks. I bought a 125 ft. 6/2 Stranded Romex , and the run is about 110' through the basement to an interior garage wall (I just followed the path of our existing romex wires to the garage wall). I have about 15' left over, and was going to leave that extra 15' of slack in the wall cavity in case we wanted to move the wall connector to another spot in the garage. If I needed to change anything, I would prefer to downsize from a 50A breaker to 40A versus installing 4AWG wire.

I have an electrician scheduled for a service call for another item, but he is booked about a month out and there is a lot of information out there on wall connectors for self-install. I just couldn't find anything on the run length limits. Thanks!
 

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mociaf9

Active Member
Oct 18, 2018
2,885
5,964
CA
for clarification, 6 GA is allowed to be connected to a 60A breaker, which will allow for a 48A EVSE. If you are installing a 50A breaker, then you would charge at 40A.
This isn't the case when using ROMEX (NM-B cable). If you're using 6ga. wire in conduit, you're fine at 60A, but for Romex the limit is lower at 55A. Since 55A breakers are non-standard, I believe that the NEC technically allows you to upsize the breaker to 60A but that doesn't lift the actual ampacity limits of the circuit which are still dictated by the Romex at 55A peak and 44A continuous, not 48A. But the EVSE doesn't allow you to configure it for a 55A circuit, only 50A or 60A, so you have to use the lower setting of 50A anyways. Might as well stick with the 50A breaker and simultaneously prevent any accidental trouble down the road.
 

sethinGR

Member
Apr 25, 2021
36
14
Grand Rapids, MI
trouble down the road.
Speaking of the future, since you got one mistake of mine, I found another possible future limitation I may have painted myself into.

I only have one electric car now (well will have in 4 days), but may eventually get a second for the wife. Like the OP, my service entrance is ~100 ft from the garage, and I finished my basement ceiling after running 6/2 NM-B across it, so adding / changing that wire isn't easy at all.

Adding load sharing I thought was going to be relatively easy just put a junction box in and connect two EVSEs to it and let them load share. But I see Tesla's sharing requires a sub-panel with two breakers, and I also now see a sub-panel requires a neutral, which 6/2 obviously doesn't have.

So I have to find out if load sharing from a 6/2 NM-B wire is possible with any EVSEs out there, hopefully I am just missing something.
 

ATPMSD

Member
Mar 12, 2021
346
357
Atlanta, GA
Since you apparently ran 6/2 NM-B you are limited to 50-amps and a 50-amp breaker, thus your maximum charging rate is 40-amps.

So what about that 2nd Wall Connector? It is my understanding that a subpanel does not need a neural if it will only provide 240v service. What is typically required is an independent ground wire (not run back to the main panel). This is something you should definitely discuss with a reputable electrician!
 
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sethinGR

Member
Apr 25, 2021
36
14
Grand Rapids, MI
It is my understanding that a subpanel does not need a neural if it will only provide 240v service.
Reading more, seems you are right. The external ground I think is only for a detached building, my garage is not detached. Regardless, when we get a second car I will definitely re-check the code.
 
Aug 22, 2021
5
1
Harrisburg, PA
Thanks for the info and links!

I have seen some of the discussions on breaker sizing, and for me it wasn't worth hunting down 4 AWG NM-B to use a 60 AMP breaker. I'll be running a second 6/2 NM-B from the breaker box for another wall connector in a year or so for a Cybertruck
 

Rocky_H

Well-Known Member
Feb 19, 2015
6,792
8,398
Boise, ID
What is the maximum length of 6/2 romex for a wall connector on a 50A breaker? Is there a chart or reference I could use?
That is an interesting one where code does not actually specify a limit on length but gives a general recommendation to not have too much voltage drop. How much is too much is kind of vague.
I use this link, which seems to indicate you can go 150-feet with 6 AWG copper wire at 50-amps

http://www.paigewire.com/pumpWireCalc.aspx
2nd reference,, this one says just under 163-feet
You can use those a few different ways, depending on what you set as limits. If you set the allowable % voltage drop pretty tight, it will cut your length pretty short. If you ease up on allowing more drop, the length can go out a lot more. And you can use it informationally by putting in the actual length you have and set the % drop high and then let it show you how many volts of loss that will have. The charger in the car is very forgiving of voltage ranges, so it can use a pretty broad range. But it will check the initial voltage and then the voltage sag when it loads up with heavy current. If that drops a lot, it will fault and show a warning that it thinks there is a problem in the circuit connection.

I think the 50A setting, running 40A continuously to the car should work fine, but if the car complains about too much voltage drop, you can turn the setting down some to around 36-38 and see if that will run fine without too much voltage sag.
 
Aug 22, 2021
5
1
Harrisburg, PA
Thanks again for the info, I was able to install and commission the wall connector without much trouble.

Interestingly, I also found that the Tesla NEMA 14-50 installation sheet for the mobile connector says "Conductors: 6 AWG copper wire for circuits up to 150 feet", so it seems to the voltage drop will be within the acceptable range.
 

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sethinGR

Member
Apr 25, 2021
36
14
Grand Rapids, MI
NEC technically allows you to upsize the breaker to 60A but that doesn't lift the actual ampacity limits of the circuit which are still dictated by the Romex at 55A peak and 44A continuous, not 48A. But the EVSE doesn't allow you to configure it for a 55A circuit, only 50A or 60A, so you have to use the lower setting of 50A anyways.
Now I wonder. As I mentioned up thread, I am buying a JuiceBox 48, and I read in their docs I can adjust the charge current limit to less than 48A, so I can set it to 44A, which would make it acceptable for use with the 6/2 NM-B, as the breaker can be as you say 60A.

Honestly, 48 vs 44 vs 40 doesn't really matter I ain't going to be draining the entire battery day after day and needing huge recharge amounts. the super-off-peak charge hours are 11pm to 6am, even at only 30 mi/hr that is 210 miles of range, should be more than enough
 

ATPMSD

Member
Mar 12, 2021
346
357
Atlanta, GA
I am buying a JuiceBox 48, and I read in their docs I can adjust the charge current limit to less than 48A, so I can set it to 44A, which would make it acceptable for use with the 6/2 NM-B, as the breaker can be as you say 60A.

You cannot set the current limit, you set the circuit capacity e.g. breaker size, and the unit internally sets the limit. For a 60A circuit this is 48A, and for a 50A circuit this is 40A. As to "upsizing" this is something you need to ask an electrician about; it does not sound kosher to me. I suggest you stick with a 50A circuit, especially given the long run you noted.
 

sethinGR

Member
Apr 25, 2021
36
14
Grand Rapids, MI
You cannot set the current limit, you set the circuit capacity e.g. breaker size, and the unit internally sets the limit. For a 60A circuit this is 48A, and for a 50A circuit this is 40A. As to "upsizing" this is something you need to ask an electrician about; it does not sound kosher to me. I suggest you stick with a 50A circuit, especially given the long run you noted.
Are you sure you are talking about the Enelx JuiceBox and not a Tesla HPWC? You could be right, as I don't have a Juicebox handy, but I was told you could adjust the current limit in a fine-grained way.

As to the upsize, I am confident in that, I asked the electrical inspector for my city and he approved it (he was the one who told me I could do it).
 

ATPMSD

Member
Mar 12, 2021
346
357
Atlanta, GA
Are you sure you are talking about the Enelx JuiceBox and not a Tesla HPWC?

Seems to be the same as the Tesla Wall Connector


It is possible, I guess, that more options are available, but I suggest downloading the manual for anything you are considering before buying.
 

sethinGR

Member
Apr 25, 2021
36
14
Grand Rapids, MI
downloading the manual
yeah, as you may have discovered, the Juicebox EVSE is controlled through their app, and the documentation for that is non-existent (that I could find). You know apps these days, they are all self-documenting. I will find out when I get the device I guess. If I have to charge at 40A, so be it.
 

Rocky_H

Well-Known Member
Feb 19, 2015
6,792
8,398
Boise, ID
As to the upsize, I am confident in that, I asked the electrical inspector for my city and he approved it (he was the one who told me I could do it).
I will clarify with the question very specifically:
so I can set it to 44A, which would make it acceptable for use with the 6/2 NM-B, as the breaker can be as you say 60A.
Are you talking about this specific situation, where using 6 gauge NM-B, "upsized" as if it were a 60A circuit? If you are saying that a city inspector approved THAT, I would get in his face to challenge him to explain that. That does not pass code. That wire can only support up to a 55A rated circuit, and you are not allowed to run that as if it's a 60A circuit.
 

sethinGR

Member
Apr 25, 2021
36
14
Grand Rapids, MI
Are you talking about this specific situation, where using 6 gauge NM-B, "upsized" as if it were a 60A circuit?
Not exactly. I am saying two things:
1. Code says 6 GA NM-B circuit is allowed to be used with a 60A breaker. I don't have the exact NEC section, but that is what he (and others) have told me.
2. Code says 6 GA NM-B circuit is allowed to carry 44A max continuous current.

From those two assertions, I deduce that if I am able to set my EVSE to limit the current to 44A, I can use that EVSE with 6 GA NM-B and a 60A breaker.
 

Rocky_H

Well-Known Member
Feb 19, 2015
6,792
8,398
Boise, ID
Not exactly. I am saying two things:
1. Code says 6 GA NM-B circuit is allowed to be used with a 60A breaker. I don't have the exact NEC section, but that is what he (and others) have told me.
2. Code says 6 GA NM-B circuit is allowed to carry 44A max continuous current.

From those two assertions, I deduce that if I am able to set my EVSE to limit the current to 44A, I can use that EVSE with 6 GA NM-B and a 60A breaker.
Ah, I see. This would be trying to forcibly create a "55" rated circuit if that is possible. 44A continuous, times the 125% overage rating would be a 55A circuit. And then code would allow for the "next size up" rule, which could put a 60A breaker on, because there's not a 55A sized one (but still literally defined as 55A rated for the whole circuit).

It's one of those things that works on paper or in conversation as a thought exercise, but this is getting into theoretical unicorn territory about something that probably can't actually be purchased or built. I don't think you will be able to find any EVSE sold by any company that can be actually permanently configured for a maximum 44A continuous, as if it were on a 55A rated circuit. The manufacturers of EVSEs know that 55A circuits don't really exist, so they will only build them with configurations for either 50 or 60.
 

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